1. Field of the Invention
The present invention relates to a lens barrel unit and an imaging apparatus.
2. Description of the Related Art
In general, in a lens barrel unit or imaging apparatus, a plurality of constituent elements must be driven to move lenses for zooming and focusing, to open/close a lens barrier that protects an objective lens, and so on. The timing of operation and the amount moved vary for each constituent element.
Conventionally, there has been publicly known a driving mechanism in which a plurality of cams are provided on a single rotating member so that the plurality of constituent elements can each be driven with a prescribed timing and by a prescribed movement amount. However, in such a mechanism using cams, there has been a problem that to make the movement amount large, a large cam must be used.
For example, Japanese Patent Application Laid-open No. 2005-128335 discloses a lens barrel unit having a driving mechanism in which a groove for opening/closing a lens barrier is provided on a cam ring having a cam groove for driving a lens. However, in the mechanism of above publication, the projected area in the direction of the optical axis becomes large, and hence this mechanism is not suitable for making the lens barrel unit small; in particular, this mechanism does not contribute to making a bending optical system that bends the optical axis through approximately 90° thin.
Hitherto, in small lens barrel units linear driving mechanisms such as screw feed mechanisms and piezoelectric actuators according to which a driving member is moved in a straight line along a driving shaft have been widely used for driving lenses and so on.
However, in such linear driving mechanisms, there has been a problem that only one linear movement can be produced, and hence it is not possible to drive a plurality of constituent elements with different timings.